Uni-Loc makes an aluminium pin that is 5.5 grams!
The only problem is that the insert required weighs 10.5....
Still not too bad at a total of 16g, but I prefer to have a radial pin and no insert so that I can thread a piece of 3/8 dowel for a "shaft-jump" handle. You can also over-bore the hole by a bit, taking more weight out of the back end of the shaft. I like the front of the cue (tip end) to be heavy, and the back end as light as possible. That combination makes getting the cueball up in the air virtually effortless, and I have jumped full balls from 1/4" away using this setup!
The only problem is that the insert required weighs 10.5....

Still not too bad at a total of 16g, but I prefer to have a radial pin and no insert so that I can thread a piece of 3/8 dowel for a "shaft-jump" handle. You can also over-bore the hole by a bit, taking more weight out of the back end of the shaft. I like the front of the cue (tip end) to be heavy, and the back end as light as possible. That combination makes getting the cueball up in the air virtually effortless, and I have jumped full balls from 1/4" away using this setup!